Storage, generation, and use of hydrogen

ABSTRACT

A composition comprising a carrier liquid; a dispersant; and a chemical hydride. The composition can be used in a hydrogen generator to generate hydrogen for use, e.g., as a fuel. A regenerator recovers elemental metal from byproducts of the hydrogen generation process.

This application claims the benefit of the filing dates of ProvisionalU.S. Patent Applications Ser. No. 60/261,616, Hydrogen Fuel StorageSlurry, Jonathan L. Rolfe et al.; Ser. No. 60/261,601, Hydrogen FuelGeneration Assembly and Method, Christopher A. Larsen et al.; and Ser.No. 60/261,600, Regeneration Assembly and Method for Converting MetalOxides and Metal Hydroxides to Elemental Metals, Ravi Konduri et al.,all of which were filed on Jan. 12, 2001, and all of which areincorporated here by reference in their entireties.

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/707,105, Disposable Hydrogen Fuel Source, filed Nov. 6,2000, which is a divisional of U.S. patent application Ser. No.09/309,198, filed May 10, 1999, now abandoned, and is incorporated byreference here in its entirety.

This invention was made with Government support under contracts awardedby the U.S. Department of Energy. The Government has certain rights inthe invention.

BACKGROUND

This invention relates to the storage, generation, and use of hydrogen.

Traditional storage technologies for hydrogen include bottled compressedhydrogen gas and bottled liquid hydrogen. The use of such technologieshas been limited because of dangers in storage and in handling andtransporting. Hydrogen gas and cryogenic liquid in storage or transporthave evidenced instability and high combustibility.

Hydrogen also has been incorporated into metal hydrides from which thehydrogen can be released by the application of water. U.S. Pat. No.4,155,712, issued May 22, 1979, to Walter G. Taschek, discloses ahydrogen generator in which water vapor is combined with a metalhydride, preferably calcium hydride (CaH₂) or lithium aluminum hydride(LiAlH₄) to release hydrogen (H₂) stored in the hydride. U.S. Pat. No.4,261,955, issued Apr. 14, 1981, to Cornelius E. Bailey, Jr., et al,describes subjecting a metal hydride, such as calcium hydride, to watervapor to generate essentially pure hydrogen.

Known hydrogen-fueled power devices include fuel cells, internalcombustion engines, and other devices.

Mixing a light metal hydride, such as lithium hydride and a reactant,such as water to produce hydrogen also produces, as a byproduct, ahydroxide of the elemental metal, lithium hydroxide. Although thegeneration of hydrogen in such a process can occur on a continuingbasis, the byproduct, i.e., the lithium hydroxide, accumulates untilremoved.

SUMMARY

In general, in one aspect, the invention features a compositioncomprising a carrier liquid; a dispersant; and a chemical hydride.Implementations of the invention may include one or more of thefollowing features. The chemical hydride has a concentration of at least40% by weight of the composition. In some examples, the chemical hydridehas a concentration of less than 75% by weight of the composition, forexample, about 61%. In other examples, the chemical hydride has aconcentration of more than 90%. The carrier liquid includes an organicliquid. The organic liquid includes mineral oil, e.g., a light mineraloil. The carrier liquid includes a hydrocarbon. The hydrocarbon includesan alkane. The alkane is selected from a group consisting of pentane andhexane. The composition is in the form of a slurry. The carrier liquidhas a viscosity in the range of about 32 Saybolt Universal seconds(S.U.s.) at standard temperature and pressure (STP) to about 100 S.U.sbut preferably about 42 S.U.s. to about 59 S.U.s. The carrier liquidexhibits a flash point in the range of about 100° C. to about 350° C.and preferably about 154° C. to about 177° C.

The chemical hydride includes a light metal hydride. The light metalhydride is selected from the group consisting of lithium hydride,lithium borohydride, lithium aluminum hydride, sodium hydride, sodiumborohydride, sodium aluminum hydride, magnesium hydride, and calciumhydride. The chemical hydride includes lithium hydride.

The dispersant comprises a triglyceride. The triglyceride includes atriglyceride of oleic acid. The triglyceride includes triolein. Thechemical hydride includes magnesium hydride.

In general, in another aspect, the invention features a method thatincludes mixing chemical hydride particles and an oil to form a slurry.

In general, in another aspect, the invention includes a compositioncomprising a mass of chemical hydride particles in a concentration ofabout 90-95% by weight of the composition, and an oil coating thechemical hydride particles, the oil comprising 5-10% by weight of thecomposition.

In general, in another aspect, the invention features apparatuscomprising: a reservoir containing a chemical hydride, and a mechanismconfigured to introduce a reactant to selected different portions of thechemical hydride to effect hydrogen generating reactions at differentlocations within the reservoir.

Implementations of the invention may include one or more of thefollowing features. The reservoir includes a canister. The reservoirincludes chambers that contain chemical hydride. The mechanism includesconduits that have open delivery ends arranged to introduce the reactantto respective selected portions of the chemical hydride. The conduitsare arranged in parallel. The ends are located at different distancesalong an axis of the reservoir. The mechanism is configured to bemovable relative to the chemical hydride contained in the reservoir. Theconduits comprise needles. The mechanism includes a valving system thatcontrols the introduction of the reactant to the different portions. Thereservoir includes an exit for hydrogen generated in the reaction.

In general, in another aspect, the invention features a hydrogen fuelgeneration assembly that includes: (a) a reservoir for a slurrycomprising a carrier liquid, a triglyceride dispersant, and a chemicalhydride; (b) a reservoir for water; (c) a hydride reactor incommunication with said slurry reservoir and said water reservoir andadapted to receive the slurry and water from the reservoirs,respectively, and to mix the slurry and water to effect release ofhydrogen from the slurry; (d) a tank for receiving the hydrogen fromsaid reactor and for receiving hydroxide byproduct from said reactor,and for facilitating separation of the hydrogen and the hydroxidebyproduct; (e) a heat exchanger for receiving the hydrogen from saidtank and adapted to condense water from the hydrogen; (f) a gas-liquidseparator for receiving hydrogen and water from said heat exchanger andadapted to separate the water from the hydrogen and to dispense driedhydrogen; (g) a conduit for conveying the water from said separator tosaid water reservoir; and (h) a conduit for conveying the dried hydrogento a hydrogen-fueled power-producing device.

Implementations of the invention may include one or more of thefollowing features. The reactor includes a tubular housing and a mixerfor mixing the slurry and the water. The tank is provided with an outletfor flowing hydrogen gas from the tank, and a bottom portion for thereceiving of the hydroxide byproduct. The power-producing deviceincludes a selected one of a fuel cell, an internal combustion engine,and an external combustion engine. There are also conduit means forconveying condensed water from said fuel cell to said water reservoir.The power-producing device includes a selected one of the internalcombustion engine and the external combustion engine and the assemblyfurther includes a condenser for condensing water from water vapor fromsaid engine, said condenser being in communication with means forconveying water from said condenser to said water reservoir.

In general, in another aspect, the invention includes a method forgenerating hydrogen fuel for a power-producing hydrogen-fueled device,the method includes the steps of: (a) providing a slurry comprising anorganic carrier liquid, a triglyceride dispersant, and a chemicalhydride; (b) mixing said slurry with water to effect release of hydrogenfrom the slurry; (c) removing water vapor from the hydrogen releasedfrom the slurry, to provide dried hydrogen; and (d) conveying the driedhydrogen to the hydrogen-fueled device for the production of power.

Implementations of the invention may include one or more of thefollowing features. The organic carrier liquid includes a light mineraloil. The mixing of said slurry and said water is undertaken with anauger. The water removed from the hydrogen is returned back to a sourceof the water for mixing with the slurry. Water condensed from a fuelcell is returned to a source of the water for mixing with the slurry.

In general, in another aspect, the invention features a regenerationassembly for converting metal oxides and hydroxides to elemental metals,the assembly comprising: (a) a reactor adapted to receive the metalhydroxide and carbon, and adapted to retain a molten carbon-dissolvingmetal in the reactor; (b) means for flowing gases comprising theelemental metal in gaseous form, carbon monoxide, and hydrogen from saidreactor; (c) a condenser adapted to receive the gases flowed from saidreactor and adapted to discharge carbon monoxide and hydrogen from afirst outlet and the elemental metal, metal oxide, and carbon from asecond outlet; (d) a separator adapted to receive the elemental metal,oxide thereof, and carbon from said condenser and to discharge theelemental metal in gaseous form; (e) means for flowing the elementalmetal and the carbon dissolving metal in liquid form from said reactorto said separator; and (f) means for flowing the metal oxide and thecarbon dissolving metal from said separator to said reactor.

Implementations of the invention may include one or more of thefollowing features. A second separator receives the carbon monoxide andhydrogen from said condenser, said second separator having a firstoutlet for discharging carbon monoxide and a second outlet fordischarging hydrogen.

In general, in another aspect, the invention features a method forconverting metal oxides and metal hydroxides to elemental metalsthereof, the method comprising the steps of: (a) admitting the metalhydroxide and carbon into a reactor having molten carbon-dissolvingmetal therein; (b) flowing gases comprising the elemental metal ingaseous form, carbon monoxide and hydrogen from the reactor to acondenser; (c) condensing out the elemental metal and oxide thereof, andcarbon, and flowing same to a separator; (d) flowing carbon monoxide andhydrogen from the condenser; (e) flowing the elemental metal and thecarbon dissolving metal from the reactor to the separator; (f) flowingelemental metal oxide and the carbon dissolving metal from the separatorto the reactor; and (g) flowing the elemental metal from the separator.In some implementations, an inert gas is flowed into the reactor.

Other advantages and features will become apparent from the followingdescription and from the claims.

DESCRIPTION

(FIGS. 1, 2, 3, and 6 show hydride containers with water feed tubes.

FIG. 4 is a block diagram of a hydrogen generator.

FIG. 5 is a block diagram of a hydrogen generator and a metalregenerator.

FIGS. 7 and 8 are side sectional and top views of a hydrogen generationcanister.)

The Slurry

Hydrogen fuel can be stored in a medium that takes the form of a slurry.The slurry includes a carrier liquid, such as an organic carrier, adispersant, such as a triglyceride, for stabilizing the slurry, and achemical hydride dispersed in the carrier liquid at a concentration ofat least 40 and typically less than 75%, except for a dry, non-pumpableslurry described later, in which the concentration may be higher. Thebest range can be determined experimentally. Higher percentages yieldhigher energy densities. Lower percentages are less viscous. A goodtradeoff for a slurry of LiH with light mineral oil and a triglyceridedispersant is about 61% of LiH. Above this percentage, the slurry becametoo thick to pump. Higher concentrations may be achievable by replacingLiH with MgH₂.

Typical slurries will be in the 50-70% range depending on the hydrideused. LiH slurries will likely be in the 50-61% range. A thinner slurry,with as little as 40% hydride by weight of the slurry may be useful forcertain applications.

The slurry may be safely stored and transported and the hydrogen may beeasily extracted for use as a fuel. The slurry is not highly flammableor combustible and may be safely handled, stored, and transported. Theslurry is stable at normal environmental temperatures and pressures and,because it is a liquid, can easily be pumped through conduits. Thereaction rate with the slurry is easily controlled.

The Carrier Liquid

The carrier liquid may be an organic carrier liquid, such as mineral oilor a low molecular weight hydrocarbon, such as an alkane, preferablypentane or hexane. A preferable mineral oil is a non-toxic light mineraloil which exhibits a high flash point, in the range of about 154 degreesC. to about 177 degrees C. and a viscosity in the range of about 42Saybolt Universal seconds (S.U.s.) to about 59 S.U.s.

The mineral oil is not chemically reactive with metal hydrides, producesrelatively low vapor pressure, and remains liquid through a temperaturerange of about −40 to 200 degrees C. The carrier liquid renders theslurry pumpable and, as a safe liquid, simple to store or transport. Thecarrier slows the reaction rate when water is introduced into thehydride. The use of a slurry permits easy refueling, as by simplytopping off a tank. Other carriers may work well, including carriersthat are without water bonds and preferably are without OH bonds.Silicone-based carriers may also work for slurries. Light mineral oilshave been tested successfully at percentages of 37 to 50% by weight ofthe slurry.

The Dispersant

The dispersant in the slurry may be, for example, a triglyceridedispersant, which sterically stabilizes the slurry. The triglyceridedispersant preferably is triglyceride of oleic acid, or triolein.

Triolein is not normally considered to have the properties of adispersant. Other dispersants that could be used include Hypermer LP1, apolymeric dispersant. One function of the dispersant is to attach to theparticles of chemical hydride, increasing the drag of the particle inthe carrier fluid thus helping to prevent settling. The dispersant alsohelps to keep the particles from agglomerating. The dispersant promotesthe formation of the slurry and the stabilization of the hydride intothe mineral oil.

Good dispersant concentrations range from 0.68% to 1.88% in tests. Aparticularly good percentage is 0.75%. A broader range of percentages,from about 0.5 to about 2% of the slurry could be used. Instead oftryglicerides, the dispersants could be polymeric dispersants. Acombination of triglyceride and polymeric dispersants may also be used,and may be particularly useful if the hydride is magnesium hydride.

Dispersants sometimes have surfactant properties that may also be usefulin the formation of the slurry.

The Chemical Hydride

U.S. patent application Ser. No. 09/309,198, filed May 10, 1999, andincorporated by reference in its entirety, discloses hydrogen-containingmaterial, such as lithium hydride, lithium aluminum hydride, calciumhydride, sodium hydride, magnesium hydride, and others, for contact witha reactant, such as water, to produce hydrogen.

The chemical hydride in the slurry may be a light metal hydride, such aslithium hydride, lithium borohydride, lithium aluminum hydride,magnesium hydride, calcium hydride, sodium hydride, sodium borohydride,and sodium aluminum hydride, all of which react with water to producehigh purity hydrogen.

Examples of reactions are:LiH+H₂O→LiOH+H₂LiBH₄+4H₂O→LiOH+H₃BO₃+4H₂MgH₂+2H₂O→Mg(OH)₂+2H₂CaH₂+2H₂O→Ca(OH)₂+2H₂NaBH₄+4H₂O→NaOH+H₃BO₃+4H₂The hydrides are finely ground before being mixed with the othercomponents of the slurry. The particles of the slurry are between 5 and10 microns in diameter.

To make the slurry, we start with a powder form of hydride. This powderis first combined with a mixture of the mineral oil and dispersant. Thenthe mixture is ground in a grinder to further reduce the size of theparticles. The final particles were measured to be primarily between 5and 10 microns in diameter.

The hydrogen generation capability of the above hydrides when reactedwith water is outstanding. For example, the volume of H₂ produced bycomplete hydrolysis of 1 kg. (2.2 lb.) of lithium hydride is 2800 liters(99 ft³), and by complete hydrolysis of 1 kg of lithium borohydride is4100 liters (145 ft³).

Characteristics of the Slurry

In summary, pumpable mixtures (slurries) can usefully have proportionsof components that are 40-75% hydride (but see the later discussionconcerning dry slurries having greater concentrations), 28-59.5%carrier, and 0.5 to 2% dispersant. A particularly good mixture is 60%lithium hydride, 0.75% triglyceride, and 39.25% light mineral oil.

Slurries of the kind described here (with hydride concentrations lessthan about 0.75%) have a liquid-like flow characteristic and may be usedin generation processes that involve continuous formation and extractionof hydrogen. In such processes, the slurry can be continuouslyintroduced into a tank, while a portion of the slurry is continuouslydrawn off and subjected to water to release hydrogen. The reaction maybe stopped and started quickly and repeatedly without sacrificingcontrol of the reaction or safety.

The oil in the slurry protects the hydride from unintentional contactwith moisture in the air and renders the hydride pumpable: The slurry,when in the form of a continuing stream, provides a path for dissipatingheat generated from the hydride/water reaction. That, in conjunctionwith control of surface chemistry of the carrier liquid, permits easycontrol of the hydride reaction rate. In a continuous process, thehydrogen production rate is controlled by the injection rate of waterand hydride.

Because the oil inhibits water access to the hydride, it controls therate of reaction, which otherwise could be explosive. The dispersantmaintains the hydride particles in suspension. The dispersant attachesto the particles and fends off adjacent particles to preventagglomeration of the particles. The mineral oil protects the particlesfrom unintentional reaction with water. The amount of the dispersant andthe size of the hydride particles control the viscosity of the slurry.

The slurry burns only if high heat is applied, as by a blow torch, andmaintained. Upon removal of heat, the burning of the slurry ceases andflames die out.

Alternative Dry Slurry

An alternative hydrogen storage medium would be in the form of a dryslurry comprising 90%-95% hydride. When a drop of water is injected intoa mass of dry slurry in a test tube, a volume of about 1 cubiccentimeter of the hydride around the droplet reacts with the water,releasing hydrogen. Some of the water flashes to steam and the steamreacts with hydride as it escapes the tube with the released hydrogen.

As shown in FIG. 1, this effect can be exploited by packing dry hydrideslurry 102 into a tube 100 and pulling a needle 104 (which had beenplaced in the tube when it was packed) out of the tube whileintermittently passing water droplets through the needle. Each waterdroplet would then strike fresh hydride until the needle is fullywithdrawn.

As shown in FIG. 2, an alternate configuration would be to locateneedles 106 strategically throughout (e.g., along the length of) a largemass of dry hydride or in tubes 108 of hydride (only one tube is shownin FIG. 2). A valve 110 would then be controlled to selectively putwater droplets into different parts of the mass or into different partsof the tube to produce hydrogen as required. This arrangement would havethe advantage of requiring only one moving part, the valve, and wouldprovide the opportunity to control where the heat is being generated andhow the heat of reaction is dissipated.

As shown schematically in FIG. 3, another configuration would useseveral parallel needles 120 with ends 122 located at differentdistances along the length of a tube of hydride 124. As the water dropsare supplied simultaneously to all of the needles of the set, hydridewould be reacted along the tube at several locations. Then the set ofneedles would be moved outward 125 along the centerline 126 of the tubeso that the ends 122 are in contact with new hydride slurry. Thisconfiguration reduces the distance that must be traversed by any oneneedle. Because reacted hydride 128 will exist downstream of the lowerneedles, a path of egress 132 must be provided for the generatedhydrogen and steam. The path could be provided by non-reacting porousmaterial 130 positioned along the wall of the hydride tube far enoughaway from the centerline of the tube so that all the water vapor isconsumed in reaction with hydride before the gases reach the porouswall. Then only hydrogen would be conducted along the porous material toan outlet end 134.

The oil in the dry slurry coats the hydride particles and reduces therates of reactions with the slurry.

The Hydrogen Generator

As shown in FIG. 4, a wet slurry can be used to generate hydrogen in ahydrogen fuel generation assembly 8 that includes a reservoir 10 for theslurry, a reservoir 14 for water, and a hydride reactor 18. The waterand slurry are delivered by pumps 16, 12 to the reactor 18, which mixesthe slurry and water to release hydrogen. A tank 26 receives thehydrogen and hydroxide waste from the reactor, and separates thehydrogen from the hydroxide byproduct. A heat exchanger 32 receives thehydrogen (and associated water vapor) carried in conduit 30 from thetank and condenses the water.

A gas-liquid separator 40 receives hydrogen and water carried in line 34from the heat exchanger, separates the water from the hydrogen, anddispenses dried hydrogen and water in discrete streams 44, 42. (Thewater that is carried in conduit 34 is partly in droplet form, andpartly in liquid stream form.) The water from the separator is conveyedto the water reservoir 14 (or to water flowing from the reservoir to thereactor) through conduits 42, 36, and the dried hydrogen is conveyed toa hydrogen-fueled power-producing device 38, such as a fuel cell.

In FIG. 4, the hydride reactor 18 includes a tubular member 20 housing amixing device, such as an auger 22, rotatable in the housing. Othermixing devices could also be used including ultrasonic mixers orvibratory mixers.

The amount of water pumped to the reactor 18 is more than is needed tocomplete the release of hydrogen from the slurry. The excess water isconverted to steam and carries heat produced in the reaction out of thereaction chamber, thus controlling the temperature of the reaction.

The tubular member 20 may be fixed to, or otherwise in communicationwith an inlet 24 of the tank 26. In tank 26, the hydroxide solidmaterial falls to the bottom 28 for removal by way of an outlet 29.

When the hydrogen-fueled power-providing device is a fuel cell 38, watercondensed from the exhaust of the fuel cell is also returned to thewater reservoir 14, or to the water flowing from the reservoir to thereactor.

When the hydrogen-fueled power-providing device 38 is an internal orexternal combustion engine, the assembly also includes a condenser 46that accepts water vapor from the device 38 through a conduit 48 andcondenses water. The condensed water passes through conduit 50 into theconduit 38 for return to the water reservoir 14 (or water flowing fromthe reservoir into the reactor 18).

Thus, hydrogen suitable for use with fuel cells or engines, for example,is generated by providing a slurry including an organic carrier liquid,such as a light mineral oil, a triglyceride dispersant, and a chemicalhydride, such as lithium hydride, mixing the slurry with water torelease hydrogen from the slurry, controlling the reaction temperatureby vaporization of water, condensing water from the hydrogen releasedfrom the slurry, and conveying the dried hydrogen to the hydrogen-fueledpower-producing device.

The slurry may be prepared at centralized plants, where it is readilypumpable into tank trucks or through pipes to distribution centers wherethe slurry can be pumped into tanks of vehicles powered by hydrogen fuelcells, or into slurry reservoirs of homes or business and industrialfacilities. The hydroxide byproduct of the hydrogen production reactionmay be picked up upon the next delivery of slurry is made andtransported back to a regeneration plant, where the hydroxide will beseparated from the mineral oil and will be regenerated to hydride, asexplained below.

Other Techniques for Distributing Water to the Hydride

As shown in FIG. 6, another method of distributing water to the hydridein a chamber is through needles placed in hydride tubes in locationsthat permit water droplets that pass through needles to react withenough of the hydride to release more than 90% of the potentialhydrogen. Several needles could be placed along the length of each tube.Water would be delivered first to the needle 154 that is farthest fromthe exit of the tube 156. This water would react with the hydride aroundit. Some of the water would be evaporated and would travel throughunreacted hydride causing further reaction along the tube. A valvingsystem 158 would be incorporated with the tubes of hydride to deliverwater to the needles selectively. A computer control system 160 wouldrecord which needles had already delivered water and would selectneedles that had not delivered water for future hydrogen release.

The system of FIG. 6 overcomes the blockage of water and hydrogen flowto all portions of hydride by the metal hydroxide byproduct that isformed during the reaction. By selecting the sequence of tubes andneedles for water injection, water is delivered only to fresh hydride.The arrangement of FIG. 6 also allows the heat released from thereaction in one tube to be dissipated from the tube while another tubein the system is reacting with water to deliver hydrogen. By causing thereactions to occur in different tubes, the heat of reaction on one tubecan dissipate to the environment while slurry and water are reacting inanother tube to continue to produce hydrogen. The system may be designedso that the heat in one tube is dissipated before another reaction musttake place in that tube. This will control the temperature of the tubeand the materials within the tube.

Alternatively, the needles could be retractable from the tubes in amanner similar to that shown in FIG. 3.

Small Scale Implementation

In a small scale implementation, shown in FIGS. 7 and 8, the watersupply tubes 170 are buried in a bed 172 of chemical-hydride slurry insuch a manner that each supply tube will provide enough water to reactwith the chemical hydride near the outlet 174 of the tube. Water isstored in chambers 176 located around the perimeter of a canister 180that holds the lithium hydrid tubes 182. A valve 177 sequentiallydirects charges of water to each successive region of chemical hydride.The valving mechanism could be based on inkjet technology. Water chargeswould be supplied when the pressure in the canister drops below a setvalue. In this manner, the pressure in the canister will be cycledbetween a high value of about 200 psi and a low value of about 50 psi.The generated hydrogen exits the canister through conduit 183 afterpassing through a carbon filter 184.

The hydrogen produced could be consumed by an attached fuel cell as fastas it is generated and the electricity produced by the fuel cell may bestored in a battery or capacitor.

By supplying discrete charges of water sufficient to react with thechemical hydride within a specified diameter of the release location,the reaction within the canister 176 can be controlled so that there isnever a surplus of water. As the chemical hydride reacts with water, itsvolume increases. This increased volume occupies the storage volume ofthe water that is consumed, to achieve a minimum system volume. Flexiblewalls 190 enable the water supply chambers and the hydride tubes tochange volume as needed.

The Hydrogen Regenerator

The hydroxide byproduct can be processed to regenerate its elementalmetal component. The metal can then re-used in the hydride fuelgenerating process by hydrogenating the elemental metal to produce thehydride fuel.

As shown in FIG. 5, the hydrogen generation assembly is similar to theone shown in FIG. 4 and includes a reactor 210 and inlet tubes 212, 214which convey slurry and water, respectively, to the reactor 210. Thereactor 210 includes a tubular portion 216 housing an auger 218 formixing the slurry and water to effect release of hydrogen gas (H₂) fromthe slurry. A reactor tank portion 219 receives the hydrogen gas andsolid matter from the auger 218. The hydrogen gas moves toward a topportion 220 of the reactor tank portion 219 and is carried by a conduit222 to a separator (not shown) for drying the hydrogen. The hydroxide,which is a wet solid dust 224, falls to a bottom portion 226 of thereactor tank portion 219, from which it is removed and conveyed bytransport means 223 to a mixer 228. Mixer 228 receives carbon through aconduit 234 and mixes the carbon with the hydroxide.

The conduit 234 introduces the carbon, in solid or fluid form, such ascoal in pellet or powder form, biomass, or graphite, to the mixer 228.The mixed carbon and hydroxide are transported by transport 229 to asecond reactor 230 where there is disposed a molten pool 232 of carbondissolving metal, such as iron, nickel, manganese, and alloys of thosemetals. The metal, because of its high heat capacity and thermalconductivity, provides superior heat transfer characteristics.

Alternatively, the mixer 228 may be omitted and the carbon and hydroxidefed directly into the reactor 230.

The intermixed carbon and hydroxide particles form a layer 238 in thereactor 230, the layer 238 descending into a layer 236, and then sinkinginto the pool of molten carbon dissolving metal 232. In layer 236,decomposition of hydroxide into oxide and water vapor occurs. In layer232, the reaction between carbon and metal oxide produces elementalmetal and carbon monoxide.

In one example, the hydroxide is lithium hydroxide (LiOH) and thecarbon-dissolving metal is iron (Fe). The lithium hydroxide and carbonintroduced into the second reactor 230, forms the upper layer 328 whichdescends in the reactor 230 and in the area of layer 236 produceslithuim oxide (Li₂O), water (H₂O), hydrogen (H₂) and carbon monoxide(CO). The hydrogen (H₂) and carbon monoxide (CO) rise toward the top ofthe reactor 230. Lithium oxide (Li₂O) and carbon (C) sink into themolten pool of iron (Fe) where they produce lithium metal (2Li), carbonmonoxide (CO) and iron. (Fe).

In the molten layer 232, lithium gas (Li) is also produced, which risesto the second reactor upper portion 238. Liquid lithium (Li) and iron(Fe) pass from the second reactor metal pool 232 to a separator 240through a conduit 242. The gaseous lithium (Li) in the upper portion 238of the reactor 230, along with hydrogen (H₂) and carbon monoxide (CO),pass through a conduit 246 to a condenser 244. Condenser 244 separatesout carbon, lithium, and lithium oxide, which, in solid/liquid form,pass into the separator 240 through a conduit 248. The condenser 244discharges carbon monoxide and hydrogen gas through a conduit 250 toanother separator 258, which separates the carbon monoxide from thehydrogen.

In the separator 240, the lithium (Li) is evaporated and releasedthrough conduit 252 in vapor form, while the lithium oxide (Li₂O), inliquid form, is passed through conduit 254 to the molten metal pool 232in the second reactor 230. The lithium discharged by the separator 240and the hydrogen discharged by the separator 258 may be recycled for usein the hydride slurry.

Pumps may be used in the assembly as needed. For example, the conduits242, 254 may have magneto-hydrodynamic pumps for pumping molten metal.The molten metal pool 232 may be maintained at a temperature of at least1500° Kelvin, somewhat above the melting temperature of carbon saturatediron (1430° K). Alloys can be used to tailor the temperature.

The operating temperature of the second reactor 230 is maintained lowerthan would otherwise be required by continuously introducing into themolten pool 232 an inert gas, such as argon, through an inlet 256. Thelithium concentration in the lower layer 232 of the reactor 230 is thusmaintained at a low level. The continuous use of the inert gas tilts thethermodynamic equilibrium in favor of the lithium, allows the operatingtemperature to be reduced significantly and achieves higher yields atlower temperatures. Without the inert gas, the second reactor 230 wouldhave to be maintained at about 1850° K to obtain the same yield as 1500°K with the inert gas. The temperature in the second reactor 230 may alsobe influenced by using an iron alloy such as iron-manganese (FeMn).

When the carbon components are introduced directly into the reactor 230,they may include natural gas, which is flowable into the reactor 230through inlet 256 or a similar inlet.

In accordance with a further feature of the invention, there is provideda method for converting metal oxides and hydroxides to the elementalmetals thereof.

The assembly and method provide for a substantially closed-loopconversion, without discharge of harmful elements into the atmosphere.

Other embodiments are within the scope of the following claims. Forexample, elemental metals other than lithium may be recovered, such assodium and potassium. Alkaline-earth metals, such as magnesium andcalcium, could also be recovered.

1-22. (canceled)
 23. Apparatus comprising: a reservoir containing achemical hydride, and a mechanism configured to introduce a reactant toselected different portions of the chemical hydride to effect hydrogengenerating reactions at different locations within the reservoir. 24.The apparatus of claim 23 in which the reservoir comprises a canister.25. The apparatus of claim 23 in which the reservoir includes chambersthat contain chemical hydride.
 26. The apparatus of claim 23 in whichthe mechanism comprises conduits that have open delivery ends arrangedto introduce the reactant to respective selected portions of thechemical hydride.
 27. The apparatus of claim 23 in which the conduitsare arranged in parallel.
 28. The apparatus of claim 27 in which theconduits are located at different distances along an axis of thereservoir.
 29. The apparatus of claim 23 in which the mechanism isconfigured to be movable relative to the chemical hydride contained inthe reservoir.
 30. The apparatus of claim 16 in which the conduitscomprise needles.
 31. The apparatus of claim 23 in which the mechanismincludes a valving system that controls the introduction of the reactantto the different portions.
 32. The apparatus of claim 23 in which thereservoir includes an exit for hydrogen generated in the reaction. 33.The apparatus of claim 23 in which the chemical hydride is dispersed ina carrier liquid at a concentration of about 40-75% by weight of thecomposition.
 34. The apparatus of claim 23 in which the carrier liquidcomprises an organic liquid.
 35. The apparatus of claim 23 in which thechemical hydride comprises a light metal hydride.
 36. The apparatus ofclaim 35 in which the light metal hydride is selected from the groupconsisting of lithium hydride, lithium borohydride, lithium aluminumhydride, sodium hydride, sodium borohydride, sodium aluminum hydride,magnesium hydride, and calcium hydride.
 37. The apparatus of claim 33also including a triglyceride acting as a dispersant.
 38. The apparatusof claim 23 in which chemical hydride comprises lithium hydride.
 39. Theapparatus of claim 23 in which chemical hydride comprises magnesiumhydride.
 40. The apparatus of claim 23 in which the reactant compriseswater. 41-62. (canceled)